In a vehicle equipped with an automatic transmission, a shifter lever mechanism is typically pivotable over a series of positions representative of desired transmission gears such as, for example, park (P), reverse (R), neutral (N), drive (D), and low gear (M). The shifter mechanism is connected to the motor vehicle automatic transmission by a suitable mechanical and/or electronic operating linkage to effect actuation of the transmission to the selected gear when the shifter lever is pivoted to the transmission gear's representative position. The shifter mechanism is typically provided with a detent assembly which releasably holds the shifter lever mechanism in a desired position to prevent inadvertent movement to other positions but permit desired movement to other positions. The detent assembly typically includes a mechanical actuator which is manually operated to release the detent assembly and permit manual pivoting of the shifter lever mechanism to a new position.
Attempts have been made to replace the mechanical actuator with an electronic actuator. For example, see U.S. Pat. No. 5,220,984, the disclosure of which is expressly incorporated herein in its entirety by reference. This shifter mechanism attempts to simplify construction by providing an electrically actuated detent assembly having a locking pawl moved by an electric solenoid.
While prior electronic shifter mechanisms may eliminate the need for a mechanical actuator, they typically have very poor preload capability. When the shifter lever is slightly pushed or pulled before the detent assembly is electrically actuated, the locking pawl as well as the electric solenoid are laterally loaded and the electric solenoid may not be able to overcome the friction present in the mechanism. As a result, the electric solenoid may not be able to unlock the locking pawl. To overcome this problem, the electric solenoid must be sized to provide a relatively large force and/or the locking pawl must be held in its locking position with a relatively small preload. Neither of which are desirable. Accordingly, there is a need in the art for an improved electronic shifter mechanism.